Needless to say, the main forces of the class supporting restoration in its extreme form are drawn from the ranks of restorers or authors of works teaching the grand art of resuscitating masterpieces, such men as Merimée, Vergnaud, Prange, Deon, Forni and Secco Suardo. The latter, in fact, does not hesitate to call restoration a magic art and depicts the restorer as a regular miracle-worker.
We do not propose in this chapter to follow the various methods of restoring paintings according to the character of the work, fresco, tempera or oil, but simply to indicate some of the restoration processes that are useful to fakers in deceiving inexperienced collectors.
In the case of faking up an old painting of weak or defective character, into the delusive suggestion of a work of good quality, the process consists principally of bringing the form into proper shape by veiling and toning the crude parts of the colouring. This work, the success of which chiefly depends upon the skill and versatility of the forger, is generally effected by first removing the old varnish with a solvent. There are many kinds of solvents which can be used, according to the quality of the varnish, the most common, however, is alcohol. It must be very pure, containing the minimum of water. Ordinary alcohol is likely to produce opaque, white patches, a phenomenon called by the French restorer chanci, and very difficult to obliterate once it has appeared. Being one of the strongest solvents and of dangerous and too rapid action at times, the alcohol is generally mixed with turpentine to the proportion of half-and-half to start with. Then, according to the greater or lesser solubility of the varnish, the proportion of alcohol is gradually increased. This mixture, called la mista by Italian antiquaries, may be substituted, as we have said, by various solvents—potash, soda, ammonia, etc.—according to the nature or hardness of the varnish to be dissolved. Some restorers also resort to mechanical methods to remove old varnish. These methods, too, are various. If the varnish is hard it can be cracked by pressure from the thumb, a long operation requiring no small amount of patience and skill. If it possesses sufficient elasticity to withstand this process, it is generally removed with a steel blade in the form of an eraser. The latter operation is not only very difficult but very slow, particularly when the painting possesses artistic qualities that must not be impaired by the removal of the varnish.
This first operation successfully accomplished, the artist steps in and proceeds to help the work, say of such and such a school, to resemble the painting of the master of this school as much as possible. The process is naturally executed by the aid of a more or less complete collection of photographs of the work of the master the faker intends to imitate. The retouching may follow the most varied methods. To take the most common case, that of oil painting, the new work can be carried out with oil colours previously kept on blotting-paper to drain off the oil which is then substituted with turpentine to give the colours their lost fluidity; it may also be effected with tempera colours or with colours the fluid element of which consists only of varnish. The use of tempera is preferred by restorers because, although it presents the extreme difficulty of changing hue when varnished and consequently demands no little experience to judge the requisite hue or tone, still once laid down it is not likely to change with time as oil retouching on old paintings generally does. The mixing of colour with varnish alone has the advantage of keeping the proper tone from beginning to end. This method is extremely useful not only in the painting of missing parts but also to veil and tone what has been painted in tempera if this is not entirely harmonious with the rest after varnishing. Needless to add, those colours the fluid part of which is supplied by varnish are unalterable as they do not contain any oil whatever. One of the difficulties in handling these pigments is the lack of fluidity, hence turpentine may be added with advantage.
However, as the above methods of retouching are not proof against chemical tests, alcohol being the proper solvent with which to do away with added touches to old paintings which have been done with either oil or varnish colours, the shrewder fakers either mix amber varnish with the colours or give the fresh touches a solid coating of this varnish, which when well prepared is supposed to be insoluble and not easily acted upon by solvents. Although more than one special work on the art of restoring gives recipes for the preparation of this varnish, in practice very few know how to prepare it in the proper way.
We have here presupposed that the picture was in good order, that there were no missing parts of importance, or rather that, with panel or canvas unimpaired, the work only required to be retouched by the artist, a rare case, as when the paint has vanished the preparation of the panel or canvas has generally vanished with it, on account of its adhesiveness.
We do not propose to give the various recipes for the plaster dressing forming the preparation of the panel or canvas. They are different according to time and country and can be found in special works on painting. Under ordinary conditions it is very easy to substitute the missing preparation, just as it is easy to give it the proper surface either by pumice or skilled coating with the brush, but in the case of a painting on canvas it is very seldom that there are not big holes right through it. The first operation in such cases is to recanvas the work, to line it, namely, with another canvas which is pasted to the old one and flattened with an iron till perfectly dry. The missing part must then be filled in, imitating the weave of the canvas on which the work is painted. No easy matter this, as the different weaves of canvases are as characteristic as signatures: no two are ever alike. The new canvas showing through the hole is therefore either covered with a patch of canvas taken from some comer of the painting to be restored, or it is given the same appearance by pressing a piece of the old canvas upon the fresh preparation of the part missing, thus moulding the texture of the threads. This must be done skilfully in such a way that the parallel lines of the threads match. There are some clever fakers who imitate the old canvas by strokes of a hard brush upon the fresh preparation of the new pieces, reproducing the characteristics of the canvas by actually copying from the original part.
When a painting is finished there are various methods by which an appearance of age may be given or restored to it. From asphalt to liquorice hundreds of things are used, either dissolved in turpentine or water, glue, albumen, etc. Veiling with varnish, coloured with the proper pigment, generally gives the finishing touch.
The imitation of old and cracked varnish is simple enough. First one must give the canvas a coat of diluted glue, then varnish before the glue is quite dry. As the underlayer of glue dries quickly and has a shrinking capacity disproportionate to that of the varnish, it is easy to understand that the result will be a cracking of the varnish. A close or a coarse network of cracks is obtained by increasing or decreasing the inequality of shrinkage between the two layers, or by hastening or retarding the drying of the upper layer by artificial means. Although comparatively easy, these operations nevertheless demand no little experience to be crowned with due success.
If a painting has been repainted only in the parts that were missing, and the old varnish has not been removed from the rest of the picture, it is a question of not only giving the varnish of the new spots cracks like the old varnish, but these must imitate as closely as possible those of the original part of the painting. In such cases a needle is used to make the cracks on the newly varnished parts. When the grooves have been made in the varnish they are filled in with water and colour or soot to give them the desired appearance of age.